1. Field of the Invention
The present invention relates to a magnetic structure for use in, for example, a magnetic head of a magnetic read/write apparatus, the magnetic structure including two magnetic layers ferromagnetically coupled to each other, and to a method of manufacturing such a magnetic structure.
2. Description of the Related Art
Higher recording density is constantly required of a magnetic read/write apparatus such as a magnetic disk drive so as to achieve a higher storage capacity and smaller dimensions. Typically, a thin-film magnetic head for use in a magnetic read/write apparatus has a structure in which a read head having a magnetoresistive element (hereinafter also referred to as an MR element) for reading and a write head having an induction-type electromagnetic transducer for writing are stacked on a substrate. The induction-type electromagnetic transducer includes a coil that generates a magnetic field corresponding to data to be written on a recording medium, and a pole layer that allows a magnetic flux corresponding to the magnetic field generated by the coil to pass and generates a write magnetic field for writing the data on the recording medium.
Examples of the write head include those of a longitudinal magnetic recording system wherein signals are magnetized in the direction along the plane of the recording medium (the longitudinal direction), and those of a perpendicular magnetic recording system wherein signals are magnetized in the direction perpendicular to the plane of the recording medium. Recently, a shift from the longitudinal magnetic recording system to the perpendicular magnetic recording system has been promoted in order to achieve higher recording density of magnetic read/write apparatuses.
An example of a method of manufacturing a magnetic head will now be described. In this method, first, components of a plurality of magnetic heads are formed on a single substrate to thereby fabricate a magnetic head substructure in which a plurality of pre-head portions that will become the respective magnetic heads later are aligned in a plurality of rows. Next, the substructure is cut into a plurality of head aggregates each of which includes a plurality of pre-head portions aligned in a row. Next, a surface formed in each head aggregate by cutting the substructure is lapped to thereby form medium facing surfaces of the pre-head portions included in each head aggregate. Next, flying rails are formed in the medium facing surfaces. Next, each head aggregate is cut so that the plurality of pre-head portions are separated from one another, whereby the plurality of magnetic heads are formed.
In the process of manufacture of the magnetic heads, a second magnetic layer to be ferromagnetically coupled to a first magnetic layer is sometimes formed by plating over the first magnetic layer and a nonmagnetic insulating layer. In some cases, the nonmagnetic insulating layer is disposed adjacent to the first magnetic layer without overlapping the top surface of the first magnetic layer, and in other cases, the nonmagnetic insulating layer is disposed to cover a portion of the top surface of the first magnetic layer. The nonmagnetic insulating layer is formed of an inorganic insulating material such as alumina or an organic insulating material such as a thermosetting resin. To form the second magnetic layer by plating over the first magnetic layer and the nonmagnetic insulating layer, first, an electrode film for plating is formed on the first magnetic layer and the nonmagnetic insulating layer. Then, the second magnetic layer is formed on this electrode film by plating. In this case, the electrode film may be formed of a magnetic material in order to establish ferromagnetic coupling between the first magnetic layer and the second magnetic layer. However, an electrode film made of a magnetic material is typically low in adhesion to a nonmagnetic insulating layer. Consequently, if an electrode film of a magnetic material is formed on the first magnetic layer and the nonmagnetic insulating layer, the electrode film can peel off from the nonmagnetic insulating layer during processing for forming magnetic heads from the foregoing substructure, or cracking can occur in the electrode film due to thermal stress during a writing operation.
Conventionally, when an electrode film for plating is formed over a substrate and then a magnetic layer is formed on this electrode film by plating, there is known a technique in which, in order to enhance adhesion between the substrate and the electrode film, an adhesion layer made of a nonmagnetic metal material such as Ti, Cr, Al or Ta is formed on the substrate before forming the electrode film, as disclosed in, for example, JP-A-2002-175608. This adhesion layer typically has a thickness of 5 nm to several tens of nanometers.
In the case of forming an electrode film for plating over the first magnetic layer and the nonmagnetic insulating layer as mentioned above, too, such an adhesion layer can be formed on the first magnetic layer and the nonmagnetic insulating layer before forming the electrode film, for the purpose of enhancing adhesion between the nonmagnetic insulating layer and the electrode film.
Disadvantageously, however, if an adhesion layer made of a nonmagnetic metal material and having a thickness of 5 nm to several tens of nanometers is formed on the first magnetic layer and the nonmagnetic insulating layer and then the electrode film and the second magnetic layer are formed thereon, the presence of the adhesion layer between the first magnetic layer and the second magnetic layer precludes ferromagnetic coupling between the first magnetic layer and the second magnetic layer. When the first and second magnetic layers form a magnetic path for passing a magnetic flux corresponding to the magnetic field generated by the coil in the write head, if ferromagnetic coupling between the first and second magnetic layers cannot be established due to the presence of the adhesion layer, the magnetic flux passing through the first and second magnetic layers leaks at the location where the adhesion layer is present. As a result, the write head suffers problems such as a reduction in write magnetic field and erroneous writing or erasure of data on the recording medium caused by the leakage flux.